Clubtooth lever escapement

ABSTRACT

A clubtooth lever escapement with high transmission efficiency having an escapement wheel and an anchor, and satisfying at least one of 2.0 LG/LAI 1.0 and 2.0 LG/LAD 1.0, where LG is the length of the impulse face of said escape wheel tooth, LAI is the length of the impulse face of the entry pallet jewel of said anchor and LAD is the length of the impulse face of the exit pallet jewel of said anchor.

United States Patent Kenji Abe Suwa, Japan Apr. 6, 1970 Dec. 21, 1971 Kabushiki Kaisha Suwa Seikosha Chuo-ku, Tokyo, Japan Apr. 14, 1969 Japan Inventor Appl. No. Filed Patented Assignee Priority CLUBTOOTl-I LEVER ESCAPEMENT 3 Claims, 7 Drawing Figs.

U.S. Cl 58/116, 74/ 1 .5 Int. Cl G04b 15/00 Field of Search 58/1 16,

References Cited UNITED STATES PATENTS 6/1907 Ohlson J eanm airet 1,044,054 11/1912 58/116 1,928,554 9/1933 Beehler 58/116 2,444,178 6/1948 Weinberger 58/116 X 3,425,212 2/1969 Verde 58/116 FOREIGN PATENTS 1,096,039 12/1967 Great Britain 58/1 16 342,897 H1960 Switzerlcard 58/116 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Stanley A. Wal Attorney-Blum, Moscovitz, Friedman and Kaplan ABSTRACT: A clubtooth lever escapement with high transmission efficiency having an escapement wheel and an anchor, and satisfying at least one of 2.0 a/L 1.0 and 2.0 L /L an 1.0, where L is the length of the impulse face of said escape wheel tooth, L is the length of the impulse face of the entry pallet jewel of said anchor and L is the length of the impulse face of the exit palletjewel ofsaid anchor.

PATENIEU m2] :sn 3628.327

SHEET 1 OF 3 FIG./

PATENIEU M221 2971 SHEET 2 0F 3 SUMMARY OF THE INVENTION The present invention relates to an improved clubtooth lever escapement for a timepiece and more particularly to the transmissionefficiency of the escapement. The length of the respective impulse faces of the escape wheel tooth, the entry pallet jewel and exit pallet jewel are determined in accordance with a fixed relation to increase the transmission efficiency of the whole escapement.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a plan view of a conventional clubtooth lever escapement; a

FIG. 2 shows the operating relationship between the driving part (hereinafter referred to as an escape wheel portion) and the driven part (hereinafter referred to as an anchor portion) when they rotate in one direction;

FIGS. 3 and 4 show the operating relationship between an escape wheel tooth and an entry pallet jewel;

FIG. 5 shows the operating relationship between an escape wheel portion and an anchor portion when the latter rotates in the opposite direction;

FIG. 6 is a graph showing the relationship between the mainspring torque and the amplitude of the balance in a conventional escapement and also in an escapement according to the present invention;

FIG. 7 is a graph showing the relationship between the frequency and the transmission efficiency in a conventional escapement and also in an escapement according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved clubtooth lever escapement for a timepiece. I

As is apparent from FIG. 1, a clubtooth lever escapement is composed of an escape wheel 1, and anchor 2 and a roller table 3 ofa balance. The roller table 3 is coaxially mounted on a balance staff 13. As the roller table 3 rotates in the direction of the arrow 16 with the rotation of the balance, a rollerjewel 12 strikes against a horn ll of the anchor, permitting an entry pallet jewel 7 to leave its lock face 8. As the escape wheel 1 rotates in the direction of the arrow 14, the anchor 2 receives rotation torque in the direction of the arrow 15 and transmits the energy through the horn ll of the anchor and the roller 12 to the balance. An exit pallet jewel 7' then locks an escape wheel tooth against rotation and at the same time the anchor 2 is pressed against a banking pin While the balance rotates in the opposite direction to the arrow 16, said exit pallet jewel takes the same action as said entry palletjewel.

The escape wheel tooth is provided with a lock face 5 and an impulse face 6. The entry pallet jewel 7 of the anchor is provided with a lock face 8 and an impulse face 9, while the exit pallet jewel 7' is provided with a lock face 8' and an impulse face 9'. Therefore the energy transmission from the escape wheel 7 to the anchor 2 is accomplished at the impulse faces thereof.

It has been found by observation that the transmission efficiency of the conventional clubtooth lever escapement is approximately 40 percent in a wrist watch having 18,000 to 21,600 vibrations/hour and approximately 30 percent in a wrist watch having 36,000 vibrations/hour. If the frequency is increased, kinetic loss is also increased by the quick vibration of the balance. Therefore, the balance cannot receive sufficient energy.

In the conventional wrist watch having 36,000 vibrations/hour, (1) sufficient energy is provided to its balance by an extreme increase of the mainspring torque; or (2) the amplitude of the balance is made small; that is, the potential and kinetic energy of the balance is decreased; or otherwise (3) the moment of inertia of the balance is decreased extremely, that is, the potential and kinetic energy of the balance is decreased.

Ann

(I), (2) and (3) above mentioned may be combined appropriately, but it is undesirable at any time.

In the case of l the power reserve becomes small and the torque variation of the mainspring becomes large. Further, wear resistance is poor. Therefore, extremely high precision watches cannot be obtained.

In the case of (2), there is the disadvantage that as the amplitude is decreased, positional error of the hairspring, positional error due to unbalance, escapement error and positional errors in vertical or horizontal position become increasingly greater.

In the case of (3), escapement error is extremely increased, thus making it difficult to compensate for the positional errors in vertical and horizontal positions.

The purpose of the present invention is to provide a clubtooth lever escapement having extremely high transmission efficiency by maintaining a certain relationship between the impulse face of the escape wheel tooth and that of the entry pallet jewel.

In the present invention, a timepiece having extremely high frequency and high precision can be obtained by increasing the transmission efficiency of clubtooth lever escapement.

For example, the timepiece having 18,000 to 2l,600 vibrations/hour, according to the present invention can be increased in its transmission efficiency from approximately 40 percent (conventional) to approximately 53 percent; that is, 1.3 times conventional efficiency. Furthermore, timepieces having 36,000 vibrations/hour according to the invention can be increased from approximately 30 percent (conventional) to approximately 45 percent; that is, 1.5 times, so that the kinetic and potential energy of the balance can be highly increased to make the vibration stable.

Concerning the conventional escapement, careful study has not been carried out for the improvement of the transmission efficiency.

0n the other hand, in the present invention, the escapement having extremely high efficiency above mentioned can be realized by establishing a theory as to transmission efficiency and calculating by means of a computer.

The present invention will be disclosed hereinafter by the relations between the escape wheel and the anchor as to the transmission efficiency of the escapement and calculated by the computer in the accompanying drawings.

Referring to FIG. 2, the escape wheel portion which rotates on an axis of O in the direction of the arrow rotates the anchor portion on an axis of 0 by the force F passing through the point of contact C. F represents the force without friction. 'y represents a friction angle. P, and P, is the length of a perpendicular line drawn on the extension line of the force F from O and 0 respectively. P and I" is also the length of a perpendicular line drawn on the extension line of the force F. A or B represents the distance between O and C, or between 0 and C respectively. L represents the length between O and 0 a is .CO,O 0 is O,CO and B is (l. C0,0 is an angle formed with a segment of a line 0 C and F. 6, and 6, represent angles in polar coordinates where O and O, are the origin thereof correspondingly.

Generally from FIG. 2, the transmission efficiency 1 is given by the following equation Assuming that torque of the escape wheel portion is M, we can write:

Since the emitting energy of the escape wheel side equals the absorbing energy of the anchor side under no friction, the following equation can be obtained:

Assuming that the amount of M is constant, the equations l and (2) lead to:

Further from the Equations (3) and (4),

In FIG. 2 we can 55a FIG. 3 shows the operating relationship in which the impulse face of the entry pallet jewel is lifted by the locking comer 17 of the escape wheel tooth. R, or R is the length between O and the locking corner 17 or the leaving comer 18 of the escape wheel tooth. Au is an angle formed with the segments of lines R, and R S is the length between and the locking comer 19 of the anchor. S is the length between 0, and the leaving corner 20 of the anchor. AB is an angle formed with the segments of the lines S, and S Now in order to obtain the transmission efficiency of a clubtooth lever escapement under the condition shown in FIG. 3, the following equations are substituted into the equations (6), and

Then the transmission efficiency 1) can be calculated from the equation 5.

FIG. 4 shows the operating relationship in which the impulse face of the escape wheel tooth is impelled against the leaving corner 20 of the entry palletjewel.

Under the impulse condition shown in FIG. 4, the following equations are substituted into the equations (8) and (9), and then the transmission efficiency 1; can be calculated from the equation (4).

A Hm am --0+cos" I Thus the total, static transmission efficiency 1;, of the entry pallet side can be obtained with consideration for the transmission efficiency due to impulse above-mentioned and the losses due to disengagement and dropping of the escapement.

FIG. shows the operating relationship in which the escape wheel tooth is impelled against the exit pallet jewel. As is apparent from FIG. 5, the total transmission efficiency 1 of the exit pallet side can be calculated in nearly the same manner as in the case of the entry pallet side, by employing the following equations:

Therefore, the transmission efficiency '1 between the escape wheel and the anchor is given:

where 9,, is the rotating angle of the escape whee l while the and It was found from the calculation by the-computer that the extremely high transmission efficiency could be'obtained when satisfying the following relations:

where LG= V R1 l-R2 -2R,R2COSAa is the i r n2ulsefacelength Namely, in the conventional escapement, the length of the impulse face of the escape wheel tooth is fairly shorter than that of the anchor.

As can be understood from the above description, the relations among L L, and L have not been considered in the improvement of the efficiency of the conventional escapement. In other words, the relations among L L and L as above mentioned have been employed only customarily in the conventional escapement and they have been decided regardless of the improvement of the efficiency of the escapement.

On the other hand, in the present invention, the improvement of the escapement efficiency can be performed by keeping the relations among L L, and L satisfactorily. Especially in the present invention, the transmission efficiency of the escapement can be extremely increased by making the length of the impulse face of the escape wheel equal to or greater than the length of the impulse face of the anchor.

The results of the experiment where the escapement according to the present invention is compared with the conventional one will be disclosed hereinafter only by the examples.

In this case, the conventional escapement has L /L ,=0.5" and L /L OJ," while the escapement according to the invention has L /L LT and L /L LZ." Two kinds of wrist watches with the above-mentioned escapements, which show the moment of inertia of 910 mg/mm and 36,000 vibrations/hour respectively, were compared with each other in the amplitude in the horizontal position.

The results were as follows:

TABLE I Dimension 01 escspement 0 Escepement Lo LA! LAD Lc/Lxr Lo/Lsn ?&E$lfffi::::::::::::: $23 if? 3?? iii 2% entry pallet side is operated. is that of the exit pallet side.

NOTE.Un1t0fLo, L51, LAD:

FIG. 6 shows the relationship between the amplitude and the torque in the horizontal and vertical position in the conventional escapement and the escapement according to the invention.

As a result, the ratio of the mainspring torque to the same amplitude of 210 between the conventional escapement having the torque of I20 gem. and the escapement having the torque of 80 gcm. according to the invention is l20/80=l.5, that is, the transmission efficiency in the escapement according to the invention can be increased by 50 percent.

Further, since the transmission efficiency of the train wheels is generally 70 percent and Q value of the balance is approximately 300, the transmission efficiency of the escapement can be calculated from table I. Namely, the transmission efficiency of the conventional escapement is 31 percent, while that of the escapement according to the present invention is 46 percent. In other words, the transmission efficiency of the escapement according to the present invention can be increased by approximately 1% times that of the conventional escapement.

FIG. 7 shows the transmission efficiency of the timepieces having different frequency. As can be seen from FIG. 7, the transmission efficiency of the escapement according to the invention is far higher than that of the conventional escapement. In fact, for example, in a timepiece having 72,000 vibrations/hour according to the present invention, the transmission efficiency can be increased about two times that of the conventional one. This fact makes it possible to decrease the isochronism error caused by a hairspring, positional error and escapement error. Therefore, this ensures the production of timepieces with extremely high frequency.

In the example, according to the invention, an escapement, where both entry and exit pallet jewels satisfy the relations (12) and (13) simultaneously, is shown. However, the transmission efficiency can be increased by improving either of the entry pallet jewel or the exit pallet jewel in the efficiency. Namely, the efficiency in the entry pallet jewel can be increased by satisfying the relation (l2), while the efficiency in plied without departing from the spirit thereof.

What is claimed is:

l. A clubtooth lever escapement with high transmission efficiency comprising an escape wheel having a plurality of teeth each of said teeth having an impulse face; and an anchor having an entry pallet jewel and an exit pallet jewel, each of said entry and exit pallet jewels being formed with an impulse face for cooperative engagement with said escape wheel teeth for the transmission of energy from said escape wheel to said anchor, and wherein 2.0 L IL 1.0, where L is the length of the impulse face of the escape wheel teeth, and L is the length of the impulse face of the entry pallet jewel of the anchor. 2. A clubtooth lever escapement as recited in claim 2, wherein 2.0 L lL 1.0 where L is the length of the impulse face of the exit pallet jewel of the anchor.

3. A clubtooth lever escapement with high transmission effi- I ciency comprising an escape wheel having a plurality of teeth, each of said teeth having an impulse face; and an anchor having an entry pallet jewel and an exit pallet jewel, each of said entry and exit pallet jewels being formed with an impulse face for cooperative engagement with said escape wheel teeth for the transmission of energy from said escape wheel to said anchor, and wherein 2.0 aL /L 1.0, where L is the length of the impulse face of the escape wheel teeth and L is the length of the impulse face of the exit pallet jewel of the anchor.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3.6g8.-327 -W 'Inventor(s) Kenji Abe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

Column 6', line the claim reference numeral "2 Signed and sealed this 11th day of February 1975.

(SEAL) Attest:

i I t' C. ;MARSHALL- DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks USCOMM-DC 60376-P69 w u.s. GOVERNMENT "mime ornc: I! 0-366-334.

FORM PO-105O (1M9) UNITED STATES PATENT OFFICE CERTIFICATE OF EORRECTION Patent No. 3,628,327 Dated December 21. 1971 'Inventor(s) Kenii Abe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6-, lirle 18, the claim reference numeral 2 should read --l- Signed and sealed this 11th day of February 1975.

(SEAL) Attest: v

' 1' C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks FORM PC4050 (1069) USCOMM-DC 60376-P69 U-S. GOVER NHINT HUNTING OFFICE I I9. 3'33,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PateotN 3.628.327 I Dated December 21 19 71 'Inventor(s) Kenii Abe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

Column 6', lirle I8, the claim reference numeral "2" should read 1+-.

Signed and sealed this 11th day of February 1975.

(SEAL) Attest 1' C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks USCOMM-DC 60376-969 u.s. GOVERNMENT PRINTING ornc: nu 0-in-3.

FORM FO-105O (IO-69) 

1. A clubtooth lever escapement with high transmission efficiency comprising an escape wheel having a plurality of teeth each of said teeth having an impulse face; and an anchor having an entry pallet jewel and an exit pallet jewel, each of said entry and exit pallet jewels being formed with an impulse face for cooperative engagement with said escape wheel teeth for the transmission of energy from said escape wheel to said anchor, and wherein 2.0 LG/LAI 1.0, where LG is the length of the impulse face of the escape wheel teeth, and LAI is the length of the impulse face of the entry pallet jewel of the anchor.
 2. A clubtooth lever escapement as recited in claim 2, wherein 2.0 LG/LAD 1.0 where LAD is the length of the impulse face of the exit pallet jewel of the anchor.
 3. A clubtooth lever escapement with high transmission efficiency comprising an escape wheel having a plurality of teeth, each of said teeth having an impulse face; and an anchor having an entry pallet jewel and an exit pallet jewel, each of said entry and exit pallet jewels being formed with an impulse face for cooperative engagement with said escape wheel teeth for the transmission of energy from said escape wheel to said anchor, and wherein 2.0 LG/LAD 1.0, where LG is the length of the impulse face of the escape wheel teeth and LAD is the length of the impulse face of the exit pallet jewel of the anchor. 